Method of manufacture energy absorber

ABSTRACT

This energy absorber for use on automotive vehicles has a cylinder slidably mounted in a support bracket to flex a belt of energy absorbing material on bumper impact to dissipate impact energy. The cylinder has integral radial connector straps at its outer end to facilitate bumper attachment. The belt is looped around a pair of pins, one being slidably mounted in a travel slot and the other in an end notch facilitating assembly of the belt into the cylinder. Preferably the energy absorber cylinder and connector straps are made from a one piece stamping rolled into a cylinder and seam welded.

This is a division of application Ser. No. 746,421, filed on Dec. 1,1976, now U.S. Pat. No. 4,046,411.

This invention relates to energy absorption units and more particularlyto an energy absorber having a cylindrical body with integral connectorstraps at one end for attachment to a vehicle bumper and with improvedconstruction for mounting a flexible belt of energy absorbing materialwithin the body. This invention further relates to a new and improvedmethod of making an energy absorbing unit.

This energy absorber, which is particularly adapted to mount a bumper toan automotive vehicle, is a light weight unit suitable for a wide rangeof vehicles of various sizes and weights. The energy absorberincorporates a minimum number of parts which can be easily assembledwith any suitable energy absorbing medium into a complete unit ready foruse. Basically the energy absorber has improved connection with a bumperbeam by integral and radially extending straps formed on an outer end ofan energy absorber shell preferably in the form of an elongatedcylinder. The cylinder is slidably mounted in a bracket supported byvehicle frame or unibody construction. The energy absorbing mediumyieldably connects the cylinder to the vehicle frame or unibody. Onbumper impact the cylinder strokes to flex the energy absorber so thatimpact energy is dissipated. The energy absorber in the preferredembodiment of this invention is a multiwrap belt or band of orientedplastic material which can be tailored to suit varying energy absorbingrequirements by increasing or decreasing the number of wraps of thebelt. The belt is adapted to be flexed in response to movement of thecylinder relative to a bracket or other support on vehicle bumperimpact. The belt has an elastic memory which gradually returns thecylinder and the bumper attached thereto to its original position onremoval of the impact load. The shell of the energy absorber of thisinvention may be readily made by wrapping a one piece metallic stampingcontaining longitudinally extending tap portions into a cylinder inwhich guide slots are stamped. After stamping, the cylinder is seamwelded and the tabs are bent radially to form a connection with thebumper. The looped belt is inserted within the cylinder in a preloadposition and then the cylinder is attached to the vehicle frame throughsuitable bracket structure so that it is ready for operation. Thisinvention provides a superior energy absorber mechanism for mounting abumper beam to the vehicle and which functions to effectively absorbboth frontal and corner impacts and which gradually returns the bumperto its original position after the impact load is removed.

These and other features, objects and advantages of the invention willbecome more apparent from the following detailed description and drawingin which:

FIG. 1 is a perspective view of an automotive vehicle chassis frame anda pair of energy absorber units mounting a bumper assembly to the frame;

FIG. 2 is an enlarged sectional view taken along the plane indicated byline 2--2 of FIG. 1 showing an energy absorber unit of this invention inits normal extended position;

FIG. 3 is a view taken generally along the plane indicated by line 3--3of FIG. 2;

FIG. 4 is a perspective view of a metallic blank utilized to make theouter cylindrical shell of this energy absorber.

FIG. 5 is a perspective view of the energy absorber outer shell wrappedinto a cylinder with integral mounting straps flared radially outwardlyfor mounting purposes.

Referring now to FIG. 1 of the drawing, there is a vehicle chassis frame10 comprising a pair of laterally spaced side rails 12 having forwardextending horn portions 14 interconnected by a front cross member 16.The horn portions of the frame 12 are box-like structures and havecircular openings 18 in their terminal end walls 20 to receive thetubular bodies 22 of support brackets 24 that slidably support thecylinders 26 of the energy absorber units 28. Each support bracket has aradial flange 30 to fit against the end wall 20 of the associated hornportion and each flange is formed with holes 32 that receive fastenermeans 34 which are threaded into the end walls 20 of the side rails.

The elongated cylinder 26 of each energy absorbing unit extends from aterminal position within the horn portions of the frame through thesleeve portion 22 of the bracket 24 to an outer end, terminating inthree circumferentially spaced and radially extending straps 38 whichare integral with the body portion. The straps 38 are formed with holes40 to receive the fasteners 42 that are threaded into an outer bracket44 which are secured to front bumper beam 46 by any suitable connectormeans such as the pivot structure of U.S. Pat. No. 3,700,273 issued Oct.24, 1972 to Jackson et al for "Energy Absorbing Bumper System".

In contrast to the Jackson et al patent which utilizes a hydraulic fluidmetered through an orifice for absorbing impact energy, the energyabsorbing media of this invention comprises a multilayered spring belt50 of thin oriented plastic material and preferably an orientedcopolyetherester elastomer. The belt 50 is made from an elongated stripof such material which is wound onto itself into a multilayered endlessloop. The friction properties of the belt are such that the ends of thebelt need not be secured to the adjacent belt layers although suchjoints may be accomplished by a suitable solvent if desired. The belt 50is operatively mounted in cylinder 26 by a pair of longitudinally spacedpins 54 and 56 which extend through opposite ends of the looped belt.Pin 54 is disposed in diametrically opposed pin retainer notches 58, 60formed in the terminal end of cylinder 26. Pin 56 projectingdiametrically through the sleeve of bracket 24 is disposed indiametrically opposed travel slots 62, 64 which extend longitudinallyalong the walls of the cylinder. As shown in FIG. 2 and 3 pin 56 iscradled on seats 66 and 68 formed at the inner end of the travel slots62 and 64 respectively.

On impact of the bumper beam 46, the cylinders 26 will be strokedinwardly to extend their elastic belts 50 with the pins 54 being movedwith their respective cylinders and with pins 56, fixed to the vehicleframe through brackets 24 riding in the travel slots 62 and 64.

It will be noted that inner end portions of the travel slots 62 and 64communicate by gates 70 and 72 with the end of preload slots 74 and 76respectively. The preload slots are radially offset in the samedirection, with respect to the travel slots so that they arediametrically opposed to each other to facilitate the mounting of thebelt within the cylinder in a preload condition for shipping andpackaging purposes and so that the device can be readily installed andloaded for action within the vehicle as will be later described.

When the energy absorber unit is installed in the vehicle frame thecylinder 26 is pushed inwardly until the travel pin 56 is lined with thegates 70 and 72; then the cylinder is rotated until the travel pinengages seats 66 and 68. Under these conditions, the belt is initiallydeflected and ready for energy absorbing action to provide a desirableand predictable force deflection curve which approaches the ideal squarewave curve to absorb impact energy.

As soon as the pin 56 moves from its seated position in response toinward bumper movement, the force absorbed approaches a constant valueas opposed to energy absorption by an unloaded spring device subject toinitial deflection before effective energy absorption action. After theimpact load is removed the belt, having good memory, recovers graduallyto its original shape to move the bumper outwardly ready for anysubsequent impact.

FIGS. 4 and 5 illustrate the improved method of making the light weightenergy absorbing unit of this invention. More particularly, FIG. 4 showsa generally rectilinear blank B stamped out of sheet stock with theintegral and spaced straps 38 projecting longitudinally from one endthereof. The travel and preload slots are punched out of the blankintermediate the ends thereof. End notches 58 and 60 are punched in theend of the blank opposite the strap end to provide important benefits inassembling the belt 50 into cylinder 26. The blank B is then rolled intoa cylinder and seam welded at W. After seam-welding the mounting straps38 are bent at right angles with respect to the cylinder for subsequentconnection to the bumper bracket 38. While only the cylinder 26 has beenshown with this improved method of manufacture, it will now beappreciated that this method may also be applied to make the bracket 24.

From the above it will be further appreciated that this inventionprovides a new and improved light weight energy absorber unit formounting a bumper assembly to an automotive vehicle and that only aminimum number of components are needed in this construction. Thecylinder and support bracket with integral attachment straps can bereadily stamped out of sheet metal stock with integral attaching strapsand with appropriate slots and notches rolled into a cylinder and seamwelded. The attachment straps are bent to fit mounting components.

After the parts are made the cylinder is inserted into the sleeve of thebracket. The looped energy absorbing belt is inserted into the cylinderwith pin 54 being retained in notches 58 and 60. The belt will extendlongitudinally in the cylinder past the inner end of the preload slot sothat pin 56 can be inserted in the bracket and in the preload slot tocatch the outer loop of the belt. Pins 54 and 56 are held in place bythe resiliency of the belt. In this preload condition the belt has aslight twist which is eliminated when the energy absorbing device isconditioned for operation. By holding the bracket 24 stationary andpushing inwardly on the cylinder the pin 56 is moved in the preload slotinto alignment with the gates 63. After this alignment the cylinder isturned relative to the bracket to align the travel slot with the pin 56.The cylinder is then released so that pin 56 fits against the travelslot seat 66 and 68. The belt is thus spring loaded and the energyabsorber unit is ready for automotive installation.

While the invention has been described in connection with a preferredembodiment and method, it will be appreciated that various modificationsof this construction and method can be made in light of this descriptionand without departing from the spirit of the disclosure or the scope ofthe following claims:

I claim:
 1. A method of making an impact energy absorbing unit formounting a bumper assembly to an automotive vehicle comprising the stepsof providing flat metallic stock material, blanking a generallyrectangular part out of said flat stock with a plurality of spacedlongitudinally extending and parallel straps on one end thereof, forminga pair of parallel notches in the other end of said part, forming a pairof laterally spaced slots in the flat stock in a side by side location,rolling the flat stock into a cylindrical body until the side edgesthereof are adjacent to one another and said slots are in alignment witheach other, joining said edges to one another, bending said strapsformed at one end in said flat stock outwardly of said cylindrical body,providing a bracket surrounding said cylindrical body and inserting apin through said bracket and through one end of said slots in said body,providing a pin for said notches extending across one end of said body,mounting a yieldable band around said pins to thereby provide ayieldable energy absorber unit for yieldably supporting said bumper tosaid vehicle.
 2. A method of making an impact energy absorbing unit formounting a bumper assembly to an automotive vehicle comprising the stepsof providing flat metallic stock material, blanking a generallyrectangular part out of said flat stock with a plurality of spacedlongitudinally extending and parallel straps on one end thereof, forminga pair of parallel notches in the other end of said part, forming a pairof laterally spaced and parallel slots in the flat stock in a side byside location, rolling the flat stock into a cylindrical body until theside edges thereof are adjacent to one another and said slots and saidnotches are in respective alignment with each other, joining said edgesto one another, bending said straps formed at one end in said flat stockradially outwardly of said cylindrical body, providing a bracketsurrounding said cylindrical body providing a looped belt of yieldableenergy absorbing material, inserting a pin in said belt at one endthereof, inserting said belt into said cylinder until said pin isdiametrically across one end of said cylinder and seated in saidnotches, inserting a second pin through said bracket and said travelslots to catch the other end of said belt so that said cylinder isyieldably connected to said bracket as said cylinder is longitudinallymoved with respect thereto to thereby provide a yieldable energyabsorber unit for supporting said bumper to said vehicle.